I empathize with this instinct, but I would argue that here the URLs don't really represent resources which can be moved.  Since we're dealing with an HTTP API, these URLs are really function calls.  You wouldn't generally complain about hardcoding a function call into a library.  My concern is that by making the URLs configurable, we provide a false sense of security, implying that an eventual change in the LinkedIn API could be accounted for by simply updating the configuration.  In reality, it's unlikely that a change in URL wouldn't be coincident with a change in the API that would require more substantive changes to the calling code than merely changing the URL.

As far as use of `urlparse.unparse`, I understand the instinct.  In general I only try to call out to another library if it allows more succinct code or handles cases that might not be handled by simpler, in-line code.  After examining this piece of code, though, I do see that the REDIRECT_URI might contain a query string which would need to be escaped, so that's probably a valid reason to use the library.